I have 6 black kuhli loaches- when I went to Petsmart to get them, I thought they were all out. Then the employee lifted up a rock and, zam! about a dozen of them zoomed out from under. In my 20L, I have lots of hides and they are out all the time, dancing their loach dance against the tank glass. They are absolute maniacs, and I don't think they ever sleep, lol.
I'm not familiar with the other loaches, but I know with the kuhlis, the key to get them out more is to have at least 6 and lots of hides so they feel more secure. I have heard, though, that the banded kuhlis are less out going than the black.